1. Field of the Invention
The present invention relates to a fluid valve. In particular, this invention is related to a four-way control valve with dual flow passageway for regulating hydraulic or pneumatic fluid.
2. Description of the Related Art
Four way control valves are commonly used to control a variety of mechanical devices such as linear cylinders, rotary motors or robotics actuators. In applications where precise fluid flow control are demanded, or high switching frequency are required, spool-type valve with accurate manufacturing tolerance are commonly employed. These type of valves are very expensive to build due to the tight tolerance requirements plus the need to use durable materials. Valves of these type are exemplified by the teachings of U.S. Pat. Nos. 4,611,632 to Kolchinsky, Sep. 16, 1986; 4,310,143 to Determan, Jan. 12, 1982, and 4,457,341 to Aspinwall, Jul. 3, 1984. In these type of valves, pistons are generally fixedly attached to a shaft. The shaft with the pistons are mounted within a housing. Fluid ports with predetermined locations are formed through the housing. The reciprocal movement of the shaft inside the housing allows the pistons to close and open selected fluid ports and perform the dual flow passage function. To ensure that the valve is leakproof, geometrical tolerances between pistons and housing bore are critical. Moreover, to achieve the goal of the high speed operation, piston widths relative to the fluid port opening sizes need to be precisely matched. These stringent requirements substantially increase the manufacturing cost and prevent the spool-type valves from being commonly used.
To alleviate the aforementioned shortfalls, poppet-type valves were invented in the past. A typical valve of this category is disclosed in U.S. Pat. No. 4,821,774 to Chorkey, Apr. 18, 1989. The valve normally comprises two poppets fixedly attached to a shaft. Coil springs are fastened at both ends of the shaft and the entire assembly is mounted within a housing. Fluid ports with predetermined locations are formed through the housing. The reciprocal movements of the shaft inside the housing enable the poppets to close or open selected fluid ports and perform the duty of dual flow passage. However, the monotonous movement of the shaft with fixed poppets can only avail the valve to assert the fluid traverse and reverse positions. In between the change of positions, an ambiguous transitory period appears where all fluid ports are connected together. Fluid flow directions are at a undetermined state. This period of uncertainty seriously deteriorates the valve performance in terms of operating speed and the switching frequency.
The advent of present day electronics make it possible for valve control circuitries running at a very fast speed. However, the overall operational speed of any electrol-mechanical systems is still restricted by the relatively slower mechanical parts in which control valves are key components. To optimize any electrol-mechanical design, the availability of a high-speed valve is of major importance.